After the war, Aldrin was assigned as an aerial gunnery instructor at Nellis Air Force Base in Nevada, and next was an aide to the dean of faculty at the United States Air Force Academy, which had recently begun operations in 1955. He flew F-100 Super Sabres as a flight commander at Bitburg Air Base, West Germany, in the 22d Fighter Squadron. In 1963 Aldrin earned a Doctor of Science degree in Astronautics from Massachusetts Institute of Technology.[10] His graduate thesis was "Line-of-sight guidance techniques for manned orbital rendezvous",[11] the dedication of which read, "In the hopes that this work may in some way contribute to their exploration of space, this is dedicated to the crew members of this country’s present and future manned space programs. If only I could join them in their exciting endeavors!" On completion of his doctorate, he was assigned to the Gemini Target Office of the Air Force Space Systems Division in Los Angeles before his selection as an astronaut. His initial application to join the astronaut corps was rejected on the basis of never having been a test pilot; that prerequisite was lifted when he re-applied and was accepted into the third astronaut class.

Aldrin was selected as part of the third group of NASA astronauts selected in October 1963. Because test pilot experience was no longer a requirement, this was the first selection for which he was eligible. After the deaths of the original Gemini 9 prime crew, Elliot See and Charles Bassett, Aldrin and Jim Lovell were promoted to backup crew for the mission. The main objective of the revised mission (Gemini 9A) was to rendezvous and dock with a target vehicle, but when this failed, Aldrin improvised an effective exercise for the craft to rendezvous with a co-ordinate in space. He was confirmed as pilot on Gemini 12, the last Gemini mission and the last chance to prove methods for extra-vehicular activity (EVA). Aldrin set a record for EVA, demonstrating that astronauts could work outside spacecraft.

On July 21, 1969, he became the second astronaut to walk on the Moon, keeping his record total EVA time until that was surpassed on Apollo 14. Aldrin's first words on the Moon were "Beautiful view. Magnificent desolation."[13] There has been much speculation about Aldrin's desire at the time to be the first astronaut to walk on the Moon.[14] According to different NASA accounts, he had originally been proposed as the first to step onto the Moon's surface, but due to the physical positioning of the astronauts inside the compact lunar landing module, it was easier for the commander, Neil Armstrong, to be the first to exit the spacecraft.

Aldrin, a Presbyterian, was the first person to hold a religious ceremony on the Moon. After landing on the Moon, he radioed Earth: "I'd like to take this opportunity to ask every person listening in, whoever and wherever they may be, to pause for a moment and contemplate the events of the past few hours, and to give thanks in his or her own way." He took communion on the surface of the Moon, but he kept it secret because of a lawsuit brought by atheist activist Madalyn Murray O'Hair over the reading of Genesis on Apollo 8.[15] Aldrin, a church elder, used a home communion kit given to him, and recited words used by his pastor at Webster Presbyterian Church, the Rev. Dean Woodruff.[16][17] The communion elements were the first food and liquid consumed on the Moon: in Guideposts, Aldrin stated: “It was interesting to think that the very first liquid ever poured on the moon, and the first food eaten there, were communion elements.”[18]

Later Aldrin commented on the event: "Perhaps, if I had it to do over again, I would not choose to celebrate communion. Although it was a deeply meaningful experience for me, it was a Christian sacrament, and we had come to the moon in the name of all mankind – be they Christians, Jews, Muslims, animists, agnostics, or atheists. But at the time I could think of no better way to acknowledge the enormity of the Apollo 11 experience than by giving thanks to God."[18][19]

He referred to a "Phobos monolith" in a July 22, 2009, interview with C-SPAN: "We should go boldly where man has not gone before. Fly by the comets, visit asteroids, visit the moon of Mars. There's a monolith there. A very unusual structure on this potato shaped object that goes around Mars once in seven hours. When people find out about that they're going to say 'Who put that there? Who put that there?' The universe put it there. If you choose, God put it there…"[24]

In 2011 Aldrin appeared as himself in the film Transformers: Dark of the Moon, where he explains to Optimus Prime and the Autobots that the Apollo 11 mission also discovered a Cybertronian ship on the moon whose existence was concealed from the public. In 2012, he made a cameo appearance in Japanese drama film Space Brothers.

Aldrin also lent his voice talents to the 2012 video game Mass Effect 3, playing a stargazer who appears in the game's final scene.

In 1985, Aldrin proposed the existence of a special spacecraft trajectory now known as the Aldrin cycler.[25][26] A spacecraft traveling on an Aldrin cycler trajectory would pass near the planets Earth and Mars on a regular (cyclic) basis. The Aldrin cycler is an example of a Mars cycler. He was also instrumental in the idea of training astronauts underwater in order to better prepare them for the intricate space walks and duties of maintenance while in space.

On September 9, 2002, Aldrin was lured to a Beverly Hills hotel on the pretext of being interviewed for a Japanese children's television show on the subject of space. When he arrived, Apollo conspiracy proponent Bart Sibrel accosted him with a film crew and demanded he swear on a Bible that the Moon landings were not faked, insisting that Aldrin and others had lied about walking on the Moon. After a brief confrontation, in which Sibrel called him "a coward and a liar",[27] Aldrin punched Sibrel in the jaw. The police determined that Aldrin was provoked and no charges were filed.[28] Aldrin dedicates a chapter to this incident in his autobiography Magnificent Desolation.[29]

In December 2003, Aldrin published an opinion piece in The New York Times criticizing NASA's objectives.[30] In it, he voiced concern about NASA's development of a spacecraft "limited to transporting four astronauts at a time with little or no cargo carrying capability" and declared the goal of sending astronauts back to the Moon was "more like reaching for past glory than striving for new triumphs".

In June 2013, Aldrin wrote an opinion published in The New York Times supporting a manned mission to Mars and views the moon "not as a destination but more a point of departure, one that places humankind on a trajectory to homestead Mars and become a two-planet species."[31]

In 2009, Aldrin commented on climate change by saying: "I think the climate has been changing for billions of years. If it's warming now, it may cool off later. I'm not in favor of just taking short-term isolated situations and depleting our resources to keep our climate just the way it is today. I'm not necessarily of the school that we are causing it all, I think the world is causing it."[32]

Books co-authored by Aldrin include Return to Earth (1973), Men From Earth (1989), Reaching for the Moon (2005), Look to the Stars (2009) and Magnificent Desolation (2009). He has also co-authored with John Barnes the science fiction novels Encounter with Tiber (1996) and The Return (2000). His book Mission to Mars was published in May 2013.

Aldrin has been married three times. His first marriage was to Joan Archer, the mother of his three children (James, Janice and Andrew). His second marriage was to Beverly Zile. His third marriage was to Lois Driggs Cannon, from whom he is recently divorced. He filed for divorce from Lois on June 15, 2011, in Los Angeles, citing "irreconcilable differences".[33] The divorce was finalized on December 28, 2012.[34] He has one grandson, Jeffrey Schuss, born to his daughter, Janice.

His battles against depression and alcoholism have been documented, most recently in Magnificent Desolation.[35][36] Aldrin is an active supporter of the Republican Party, headlining fundraisers for GOP members of Congress.[37] In 2007, Aldrin confirmed to Time magazine that he had recently had a face-lift;[38] he joked that the G-forces he was exposed to in space "caused a sagging jowl that needed some attention."[38]

Aldrin commented on the passing of his Apollo 11 colleague, Neil Armstrong, saying that he was "deeply saddened by the passing. I know I am joined by millions of others in mourning the passing of a true American hero and the best pilot I ever knew. I had truly hoped that on July 20th, 2019, Neil, Mike and I would be standing together to commemorate the 50th Anniversary of our moon landing...Regrettably, this is not to be."[39][40]

Aldrin is a Freemason, a member of Montclair Lodge # 144 of New Jersey and Clear Lake Lodge # 1417 of Texas.[41][42]

In 1985, Aldrin was inducted into the Scandinavian-American Hall of Fame.[44]

In 1994, Aldrin was anonymously honored on a United States postage stamp. The 29¢ stamp, commemorating the silver anniversary of the landing, was based on a famous photograph of Aldrin, captured by Neil Armstrong, in which Aldrin's face is obscured by his reflective visor. Postal rules at the time prohibited directly featuring living persons on stamps.[45]

Aldrin received the 2003 Humanitarian Award from Variety, the Children's Charity, which, according to the organization, "is given to an individual who has shown unusual understanding, empathy, and devotion to mankind."[48]

In 2005, while being interviewed for a documentary titled First on the Moon: The Untold Story, Aldrin told an interviewer that they saw an unidentified flying object. Aldrin told David Morrison, a NASA Astrobiology Institute senior scientist, that the documentary cut the crew's conclusion that they were probably seeing one of four detached spacecraft adapter panels. Their S-IVB upper stage was 6,000 miles (9,700 km) away, but the four panels were jettisoned before the S-IVB made its separation maneuver so they would closely follow the Apollo 11 spacecraft until its first midcourse correction.[52] When Aldrin appeared on The Howard Stern Show on August 15, 2007, Stern asked him about the supposed UFO sighting. Aldrin confirmed that there was no such sighting of anything deemed extraterrestrial, and said they were and are "99.9 percent" sure that the object was the detached panel.[53][54][55]

Interviewed by the Science Channel, Aldrin mentioned seeing unidentified objects, and according to Aldrin his words were taken out of context; he asked the Science Channel to clarify to viewers he did not see alien spacecraft, but they refused.[56]

^ ab"To the moon and beyond", The Record (Bergen County), July 20, 2009. Retrieved July 20, 2009. The source is indicative of the confusion regarding his birthplace. He is described in the article's first paragraph as having been "born and raised in Montclair, New Jersey", while a more detailed second paragraph on "The Early Years" states that he was "born Edwin Eugene Aldrin Jr. on January 20, 1930, in the Glen Ridge wing of Montclair Hospital".